Is there any way to establish communication between AC800M OPC DA Server and PLC Conect OPC.
Your question is self limiting. No, there is no way to exchange data between ANY two OPC servers except by some form of Bridge. ie Property Transfer or a third party OPC Bridge solution.
Your other alternative is to connect the two PLC's together directly by one of the many available bus systems, serial link protocols or IO systems.
Are you trying to execute logic statements using both AC800m OPC data and PLC Connect OPC data for HMI monitoring only? If so you can accomplish this with a calculation server which has access to both OPC data sources.
Or are you asking if its possible for an AC800m controller to access this PLC Connect OPC data and write CBM logic statments using those variables for process control? I haven't explored doing this yet; however, I would be very interested in an answer to that question myself.
Unfortunately, I suspect your available methods are likely limited to using a property transfer aspect or some other 3rd party application (gateway), like you mentioned above, to read the PLC Connect OPC variable you were interested in and then write/transfer that value to an AC800M OPC DA (read/write) variable that was created in CBM to specifically receive this PLC Connect variable. If this were to work I'd be very mindful of how to handle data quality and the potential for unreliable update rates of these varibles in the AC800m controller espeically for time critical tasks. I would also be very cautious when reading/writing to the AC800m OPCDA server since this OPC server is dedicated to controller commuinication and mistakes here could result in undesirable process control outcomes or 800xA performance impacts.